1. Field of the Invention
The present invention relates to a resin boot for constant velocity universal joint used in a state of being firmly fixed to an outer peripheral surface of a tripod joint, an outer periphery of which is formed in a convex-recess shape, in a constant velocity universal joint, for example, used in a drive shaft and a propeller shaft for transmitting a power from an engine of a motor vehicle to a tire.
2. Description of the Related Art
The tripod joint has recess portions formed in desired portions on the outer peripheral surface for various purposes such as reduction in thickness, reduction in weight and the like.
In the resin boot for constant velocity universal joint used in a state of being firmly fixed to the outer peripheral surface of the constant velocity universal joint, a bellows-shaped portion thereof plays a part in a cover and also a part in bending in correspondence to a motion of the drive shaft, the propeller shaft or the like, and an end portion thereof is firmly fixed to the outer periphery of the constant velocity universal joint via a band and plays a part in an oil (grease) seal and dust seal.
Accordingly, it is necessary to form an inner periphery of the end portion of the boots in a shape closely attached so as to be aligned with the outer periphery of the tripod joint (a joint outer race or the like), and since the tripod joint has the recess portions formed in the outer periphery thereof as described above, it is necessary that the end portion in a large diameter side firmly fixed to the outer periphery be formed to have an inner periphery having a different thickness portion.
In the past, as a boot for constant velocity universal joint used for a tripod joint, there is known a boot having a structure as shown in FIG. 24 and FIG. 25 (for example, refer to Catalogue “Constant Velocity Universal Joints or Automobiles” (CAT. No. 5601-II/JE) page 9, issued on Feb. 3, 2000 by NTN Co., Ltd).
According to the structure of the related art, the boot includes a resin bellows 100 which is formed, for example, by an injection blow molding and has a large diameter side end portion 101, having a uniform thickness, and a rubber grommet 200 which has an outer diameter fitted to an inner surface of the large diameter side end portion 101 of the resin bellows 100, is formed in a circular ring shape, and has thickness portions 201 protruding in an inner diameter direction every fixed intervals. An outer periphery of the grommet 200 independently formed as mentioned above is fit to the inner periphery of the large diameter side end portion 101 of the bellows 100. An inner periphery of the grommet 200 is fit to an outer periphery of the tripod joint 80. The boot is fastened and firmly fixed to the outer periphery of the tripod joint 80 from the outer peripheral side of the large diameter side end portion 101 by a fastening device such as a band 300 or the like.
Further, in the past, a resin grommet having thickness portions protruding in an inner diameter direction every fixed intervals is previously formed, the grommet is held within a metal mold and thereafter injection molding or blow molding of a resin bellows is executed, to thereby integrate the grommet and the bellows within the metal mold (for example, refer to Japanese Unexamined Utility Model Registration Application Publication No. 2-22463 and Japanese Unexamined Patent Publication No. 2002-286048).
However, when assembling the boot having the structure in FIG. 24 and FIG. 25 above in which the bellows 100 and the grommet 200 are independently formed and are fitted and assembled, there is a fear in that a grease may leak. That is, if the fitting operation is carelessly carried out at a time of fitting the grommet 200 to the inner periphery of the bellows large diameter side end portion 101, a displacement is generated between both elements. Alternatively, it is possible to outward fit the bellows large diameter side end portion 101 after fitting the grommet 200 to the outer periphery of the tripod joint 80, however, there is a fear in that a displacement may be generated between the bellows large diameter side end portion 101 and the grommet 200, thereby generating grease leakage.
Further, in Japanese Unexamined Utility Model Registration Application Publication No. 2-22463 and Japanese Unexamined Patent Publication No. 2002-286048, no specific technical means is provided in integrally forming the grommet and the bellows, so the both elements are not securely welded even if they are integrally formed on the surface. Accordingly, the portion which is expected to be integrally formed peels off, with the result that there is generated a problem such as grease leakage.